Medication delivery devices may have application where a person without formal medical training needs to administer accurate and/or predefined doses of a medication. In particular, such devices may have an application where medication is administered on a regular or an irregular base over a short term or long term period.
EP 1353712 A1 describes a drive mechanism for an injection device in which a ratchet means is biased by biasing means towards a further ratchet means. A drive means is actuable to drive the further ratchet means. The further ratchet means drives the ratchet means. Thereby biasing means are biased. To drive a piston rod, the ratchet means and the further ratchet means move in an angular direction.